Polyvinylidene fluoride resins are used as non-contaminating materials for parts in clean rooms and high-performance analysis devices, and the like; furthermore, they have excellent weather resistance and are also used for exterior-quality paints. Furthermore, polyvinylidene fluoride resins are also excellent in fire retardancy, and are used for fire-retardant uses that utilize advanced fire retardancy.
As an example of a foamed polyvinylidene fluoride resin body, a foamed body obtained by subjecting a polyvinylidene fluoride resin as a raw material to a crosslinking treatment, kneading a heat-decomposition blowing agent that can be decomposed at the melting temperature of the raw material resin, molding the resin into a sheet, a rod or the like, and foaming by heating, is known. Furthermore, a process of incorporating a blowing agent into a raw material polyvinylidene fluoride resin, molding the kneaded resin into a sheet, a rod or the like, and performing a crosslinking treatment to heat-expand the molding to give a foamed body, and the like are known.
For example, Patent Document 1 shows a process for obtaining a foamed article of kneading a chemical blowing agent in advance into a raw material resin obtained by electron beam crosslinking of a polyvinylidene fluoride resin, molding the kneaded resin into a sheet, and heating the sheet to decompose the blowing agent. However, only a foamed sheet that has been molded into a sheet-like shape in advance can be obtained by this process, and the degree of freedom for the shape of a foamed article obtained by this process is poor. Furthermore, there is a problem that the foamed article has poor recyclability since the raw material resin is crosslinked. Furthermore, Patent Document 2 shows foamed article of sheet and the like made of a thermoplastic fluorine resin having no crosslinked structure. Also in Patent Document 2, the obtained foamed article is sheet, and the degree of freedom for the shape of a foamed article obtained by Patent Document 2 is poor.